From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?iso-8859-1?Q?Jakob_=D8stergaard?= Subject: Re: just how dangerous is this?? Date: Tue, 28 May 2002 21:51:01 +0200 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20020528215101.E20621@unthought.net> References: <200205281055.11601.jfillman@cucbc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: ; from danci@agenda.si on Tue, May 28, 2002 at 09:20:39PM +0200 To: Danilo Godec Cc: James Fillman , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tue, May 28, 2002 at 09:20:39PM +0200, Danilo Godec wrote: > On Tue, 28 May 2002, James Fillman wrote: =2E.. > I think this shouldn't work at all - have you rebooted the machine ye= t? >=20 > It's not quite clear how the mirrors reconstruct if one of the disks > (partitions) already has a filesystem on it, but I'm almost sure it's= not > ment to reconstruct it properly... Either it reconstructs it "right" or it does it "wrong". It seems in h= is case it did it right. Lucky him. Hoever, the persistent superblocks will overwrite the last few KB of hi= s *filesystem* on each partition. So things *may* seem to work, but the system will fail horribly later. After an fsck the RAID suprblocks wil= l be damaged. After another mkraid the filesystem will be damaged again. >=20 > AFAIK making a filesystem on a Linux SW RAID array is somewhat differ= ent > from making it on a 'normal' disk, so while you may end up with a > filesystem, it will probably be full of errors. Yep. >=20 > How does your raidtab look like? >=20 > The 'right' way of doing this is: >=20 > - create a 'degraded' mirror with sda* partitions marked as 'failed' > - copy all the data from sda* partitions to the appropriate mirrors > (/dev/md*) > - modify /etc/fstab on the mirrored filesystem to use the mirrors > - reboot, use filesystems on the mirror (root=3D/dev/md?) > - hot add sda* partitions to approprate mirrors (using raidhotadd or > mdadm) > - wait for the reconstruction to finish > - make sure that both disks have the boot loader installed in MBR, so= they > can both be used for booting Yep. >=20 > This should be it. Unfortunately, this procedure is not that easy to > script. I suppose that if the installation kernel (the one booted during the in= stallation process) could be made to support RAID (with autodetection), you could = just create the RAID arrays prior to installation, and then simply install on those= arrays. But that may require some hacking of the SuSE install disk... >=20 > > the mkraid command warns me that it will delete all the data on the= partitions > > when creating the mirrors, but it doesn't. >=20 > I guess it doesn't delete the data, it destroys it... :) Just a small amount of it. It "almost doesn't totally f*ck up the syst= em" ;) >=20 > > What sort of implications am I looking at with this? Will it be uns= table? >=20 > I am no super-expert or guru, but I'd say YES. Try booting the system= with > a rescue disk and run e2fsck on your mirrored filesystems. If this go= es > through OK... Well, then I might be wrong and it's OK to do this with= new > kernel/raidtools... I'd say you're right about the failures. --=20 =2E............................................................... : jakob@unthought.net : And I see the elder races, : :.........................: putrid forms of man : : Jakob =D8stergaard : See him rise and claim the earth, : : OZ9ABN : his downfall is at hand. : :.........................:............{Konkhra}...............: - To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html